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tailscale/types/key/node.go

364 lines
11 KiB
Go

// Copyright (c) 2021 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package key
import (
"bufio"
"bytes"
"crypto/subtle"
"encoding/hex"
"errors"
"fmt"
"go4.org/mem"
"golang.org/x/crypto/curve25519"
"golang.org/x/crypto/nacl/box"
"tailscale.com/types/structs"
)
const (
// nodePrivateHexPrefix is the prefix used to identify a
// hex-encoded node private key.
//
// This prefix name is a little unfortunate, in that it comes from
// WireGuard's own key types, and we've used it for both key types
// we persist to disk (machine and node keys). But we're stuck
// with it for now, barring another round of tricky migration.
nodePrivateHexPrefix = "privkey:"
// nodePublicHexPrefix is the prefix used to identify a
// hex-encoded node public key.
//
// This prefix is used in the control protocol, so cannot be
// changed.
nodePublicHexPrefix = "nodekey:"
// nodePublicBinaryPrefix is the prefix used to identify a
// binary-encoded node public key.
nodePublicBinaryPrefix = "np"
// NodePublicRawLen is the length in bytes of a NodePublic, when
// serialized with AppendTo, Raw32 or WriteRawWithoutAllocating.
NodePublicRawLen = 32
)
// NodePrivate is a node key, used for WireGuard tunnels and
// communication with DERP servers.
type NodePrivate struct {
_ structs.Incomparable // because == isn't constant-time
k [32]byte
}
// NewNode creates and returns a new node private key.
func NewNode() NodePrivate {
var ret NodePrivate
rand(ret.k[:])
// WireGuard does its own clamping, so this would be unnecessary -
// but we also use this key for DERP comms, which does require
// clamping.
clamp25519Private(ret.k[:])
return ret
}
// NodePrivateFromRaw32 parses a 32-byte raw value as a NodePrivate.
//
// Deprecated: only needed to cast from legacy node private key types,
// do not add more uses unrelated to #3206.
func NodePrivateFromRaw32(raw mem.RO) NodePrivate {
if raw.Len() != 32 {
panic("input has wrong size")
}
var ret NodePrivate
raw.Copy(ret.k[:])
return ret
}
func ParseNodePrivateUntyped(raw mem.RO) (NodePrivate, error) {
var ret NodePrivate
if err := parseHex(ret.k[:], raw, mem.B(nil)); err != nil {
return NodePrivate{}, err
}
return ret, nil
}
// IsZero reports whether k is the zero value.
func (k NodePrivate) IsZero() bool {
return k.Equal(NodePrivate{})
}
// Equal reports whether k and other are the same key.
func (k NodePrivate) Equal(other NodePrivate) bool {
return subtle.ConstantTimeCompare(k.k[:], other.k[:]) == 1
}
// Public returns the NodePublic for k.
// Panics if NodePrivate is zero.
func (k NodePrivate) Public() NodePublic {
if k.IsZero() {
panic("can't take the public key of a zero NodePrivate")
}
var ret NodePublic
curve25519.ScalarBaseMult(&ret.k, &k.k)
return ret
}
// MarshalText implements encoding.TextMarshaler.
func (k NodePrivate) MarshalText() ([]byte, error) {
return toHex(k.k[:], nodePrivateHexPrefix), nil
}
// MarshalText implements encoding.TextUnmarshaler.
func (k *NodePrivate) UnmarshalText(b []byte) error {
return parseHex(k.k[:], mem.B(b), mem.S(nodePrivateHexPrefix))
}
// SealTo wraps cleartext into a NaCl box (see
// golang.org/x/crypto/nacl) to p, authenticated from k, using a
// random nonce.
//
// The returned ciphertext is a 24-byte nonce concatenated with the
// box value.
func (k NodePrivate) SealTo(p NodePublic, cleartext []byte) (ciphertext []byte) {
if k.IsZero() || p.IsZero() {
panic("can't seal with zero keys")
}
var nonce [24]byte
rand(nonce[:])
return box.Seal(nonce[:], cleartext, &nonce, &p.k, &k.k)
}
// OpenFrom opens the NaCl box ciphertext, which must be a value
// created by SealTo, and returns the inner cleartext if ciphertext is
// a valid box from p to k.
func (k NodePrivate) OpenFrom(p NodePublic, ciphertext []byte) (cleartext []byte, ok bool) {
if k.IsZero() || p.IsZero() {
panic("can't open with zero keys")
}
if len(ciphertext) < 24 {
return nil, false
}
nonce := (*[24]byte)(ciphertext)
return box.Open(nil, ciphertext[len(nonce):], nonce, &p.k, &k.k)
}
func (k NodePrivate) UntypedHexString() string {
return hex.EncodeToString(k.k[:])
}
// NodePublic is the public portion of a NodePrivate.
type NodePublic struct {
k [32]byte
}
// Shard returns a uint8 number from a public key with
// mostly-uniform distribution, suitable for sharding.
func (p NodePublic) Shard() uint8 {
// A 25519 public key isn't uniformly random, as it ultimately
// corresponds to a point on the curve.
// But we don't need perfectly uniformly-random, we need
// good-enough-for-sharding random, so we haphazardly
// combine raw values of the key to give us something sufficient.
s := uint8(p.k[31]) + uint8(p.k[30]) + uint8(p.k[20])
return s ^ uint8(p.k[2]+p.k[12])
}
// ParseNodePublicUntyped parses an untyped 64-character hex value
// as a NodePublic.
//
// Deprecated: this function is risky to use, because it cannot verify
// that the hex string was intended to be a NodePublic. This can
// lead to accidentally decoding one type of key as another. For new
// uses that don't require backwards compatibility with the untyped
// string format, please use MarshalText/UnmarshalText.
func ParseNodePublicUntyped(raw mem.RO) (NodePublic, error) {
var ret NodePublic
if err := parseHex(ret.k[:], raw, mem.B(nil)); err != nil {
return NodePublic{}, err
}
return ret, nil
}
// NodePublicFromRaw32 parses a 32-byte raw value as a NodePublic.
//
// This should be used only when deserializing a NodePublic from a
// binary protocol.
func NodePublicFromRaw32(raw mem.RO) NodePublic {
if raw.Len() != 32 {
panic("input has wrong size")
}
var ret NodePublic
raw.Copy(ret.k[:])
return ret
}
// badOldPrefix is a nodekey/discokey prefix that, when base64'd, serializes
// with a "bad01" ("bad ol'", ~"bad old") prefix. It's used for expired node
// keys so when we debug a customer issue, the "bad01" can jump out to us. See:
//
// https://github.com/tailscale/tailscale/issues/6932
var badOldPrefix = []byte{109, 167, 116, 213, 215, 116}
// NodePublicWithBadOldPrefix returns a copy of k with its leading public key
// bytes mutated such that it base64's to a ShortString of [bad01] ("bad ol'"
// [expired node key]).
func NodePublicWithBadOldPrefix(k NodePublic) NodePublic {
var buf [32]byte
k.AppendTo(buf[:0])
copy(buf[:], badOldPrefix)
return NodePublicFromRaw32(mem.B(buf[:]))
}
// IsZero reports whether k is the zero value.
func (k NodePublic) IsZero() bool {
return k == NodePublic{}
}
// ShortString returns the Tailscale conventional debug representation
// of a public key: the first five base64 digits of the key, in square
// brackets.
func (k NodePublic) ShortString() string {
return debug32(k.k)
}
// AppendTo appends k, serialized as a 32-byte binary value, to
// buf. Returns the new slice.
func (k NodePublic) AppendTo(buf []byte) []byte {
return append(buf, k.k[:]...)
}
// ReadRawWithoutAllocating initializes k with bytes read from br.
// The reading is done ~4x slower than io.ReadFull, but in exchange is
// allocation-free.
func (k *NodePublic) ReadRawWithoutAllocating(br *bufio.Reader) error {
var z NodePublic
if *k != z {
return errors.New("refusing to read into non-zero NodePublic")
}
// This is ~4x slower than io.ReadFull, but using io.ReadFull
// causes one extra alloc, which is significant for the DERP
// server that consumes this method. So, process stuff slower but
// without allocation.
//
// Dear future: if io.ReadFull stops causing stuff to escape, you
// should switch back to that.
for i := range k.k {
b, err := br.ReadByte()
if err != nil {
return err
}
k.k[i] = b
}
return nil
}
// WriteRawWithoutAllocating writes out k as 32 bytes to bw.
// The writing is done ~3x slower than bw.Write, but in exchange is
// allocation-free.
func (k NodePublic) WriteRawWithoutAllocating(bw *bufio.Writer) error {
// Equivalent to bw.Write(k.k[:]), but without causing an
// escape-related alloc.
//
// Dear future: if bw.Write(k.k[:]) stops causing stuff to escape,
// you should switch back to that.
for _, b := range k.k {
err := bw.WriteByte(b)
if err != nil {
return err
}
}
return nil
}
// Raw32 returns k encoded as 32 raw bytes.
//
// Deprecated: only needed for a single legacy use in the control
// server, don't add more uses.
func (k NodePublic) Raw32() [32]byte {
var ret [32]byte
copy(ret[:], k.k[:])
return ret
}
// Less reports whether k orders before other, using an undocumented
// deterministic ordering.
func (k NodePublic) Less(other NodePublic) bool {
return bytes.Compare(k.k[:], other.k[:]) < 0
}
// UntypedHexString returns k, encoded as an untyped 64-character hex
// string.
//
// Deprecated: this function is risky to use, because it produces
// serialized values that do not identify themselves as a
// NodePublic, allowing other code to potentially parse it back in
// as the wrong key type. For new uses that don't require backwards
// compatibility with the untyped string format, please use
// MarshalText/UnmarshalText.
func (k NodePublic) UntypedHexString() string {
return hex.EncodeToString(k.k[:])
}
// String returns the output of MarshalText as a string.
func (k NodePublic) String() string {
bs, err := k.MarshalText()
if err != nil {
panic(err)
}
return string(bs)
}
// MarshalText implements encoding.TextMarshaler.
func (k NodePublic) MarshalText() ([]byte, error) {
return toHex(k.k[:], nodePublicHexPrefix), nil
}
// MarshalText implements encoding.TextUnmarshaler.
func (k *NodePublic) UnmarshalText(b []byte) error {
return parseHex(k.k[:], mem.B(b), mem.S(nodePublicHexPrefix))
}
// MarshalBinary implements encoding.BinaryMarshaler.
func (k NodePublic) MarshalBinary() (data []byte, err error) {
b := make([]byte, len(nodePublicBinaryPrefix)+NodePublicRawLen)
copy(b[:len(nodePublicBinaryPrefix)], nodePublicBinaryPrefix)
copy(b[len(nodePublicBinaryPrefix):], k.k[:])
return b, nil
}
// UnmarshalBinary implements encoding.BinaryUnmarshaler.
func (k *NodePublic) UnmarshalBinary(in []byte) error {
data := mem.B(in)
if !mem.HasPrefix(data, mem.S(nodePublicBinaryPrefix)) {
return fmt.Errorf("missing/incorrect type prefix %s", nodePublicBinaryPrefix)
}
if want, got := len(nodePublicBinaryPrefix)+NodePublicRawLen, data.Len(); want != got {
return fmt.Errorf("incorrect len for NodePublic (%d != %d)", got, want)
}
data.SliceFrom(len(nodePublicBinaryPrefix)).Copy(k.k[:])
return nil
}
// WireGuardGoString prints k in the same format used by wireguard-go.
func (k NodePublic) WireGuardGoString() string {
// This implementation deliberately matches the overly complicated
// implementation in wireguard-go.
b64 := func(input byte) byte {
return input + 'A' + byte(((25-int(input))>>8)&6) - byte(((51-int(input))>>8)&75) - byte(((61-int(input))>>8)&15) + byte(((62-int(input))>>8)&3)
}
b := []byte("peer(____…____)")
const first = len("peer(")
const second = len("peer(____…")
b[first+0] = b64((k.k[0] >> 2) & 63)
b[first+1] = b64(((k.k[0] << 4) | (k.k[1] >> 4)) & 63)
b[first+2] = b64(((k.k[1] << 2) | (k.k[2] >> 6)) & 63)
b[first+3] = b64(k.k[2] & 63)
b[second+0] = b64(k.k[29] & 63)
b[second+1] = b64((k.k[30] >> 2) & 63)
b[second+2] = b64(((k.k[30] << 4) | (k.k[31] >> 4)) & 63)
b[second+3] = b64((k.k[31] << 2) & 63)
return string(b)
}